Method for manufacturing a component by a generative manufacturing process, apparatus for manufacturing a component by a generative manufacturing process, and medical implant generated for an individual patient

ABSTRACT

The invention relates to a method for manufacturing a component ( 10 ) by a generative manufacturing process, wherein the component is entirely or partially produced from a liquid raw material ( 12 ), characterised in that the component is entirely or partially produced from a liquid raw material ( 12 ) that can solidify when heated, the raw material is discharged in liquid form into a manufacturing zone ( 1 ) and heated and hence solidified by a computer-controlled, targeted light spot, in that the point of incidence of a light beam ( 8 ) from a light beam source is continuously and/or gradually modified relative to the manufacturing zone ( 1 ).

The invention relates to a method for producing a component by means ofan additive manufacturing process. The invention further relates to anapparatus for producing a component by means of an additivemanufacturing process as claimed in claim 12 and to a medical implantgenerated for an individual patient as claimed in claim 13. Inparticular, the invention relates to the field of additive manufacturingof components from liquid raw material solidifiable by heating, forexample for medical implant treatment using personalized implants.

Examples of additive manufacturing processes are stereolithography,selective laser melting, selective laser sintering, fused depositionmodeling, laminated object modeling, 3D printing and gas dynamic coldspray, especially also all manufacturing methods of rapid prototyping,of rapid tooling and of rapid manufacturing.

Polyjet modeling, digital light processing and stereolithography areknown in the field of additive manufacturing from liquid plastics, withstereolithography currently being the most accurate of all additivemanufacturing methods (J. Breuninger, R. Becker, A. Wolf, S. Rommel andA. Verl, Generative Fertigung mit Kunststoffen [Additive manufacturingwith plastics], Springer-Verlag Berlin Heidelberg, 27-28 (2013)). Thebasis of these methods is the layer-by-layer application and thelayer-by-layer structuring crosslinking of a photosensitive polymer,which is crosslinked by UV radiation. These methods are used especiallyin prototype construction, with initial methods for serial productionbeing in the course of implementation. In the area of medical implanttreatment, additive methods are subsumed under the term “medical rapidprototyping”. The methods are used for manufacturing dimensional modelsof human anatomical structures, which are created on the basis ofmedical imaging. Currently, medical rapid prototyping methods are used,inter alia, in the treatment of hard-tissue defects, such as, forexample, cranial defects, in which it is possible, with the aid ofelectron beam melting or laser sintering methods, to produce directlymatched metal cranial plates (A. D. Lantada and P. L. Morgado, Annu.Rev. Biomed. Eng. 14, 73-96 (2012)). By contrast, in the area ofsoft-tissue implants, direct additive production of medical implants isnot possible, since, currently, the polymers used here can only bemolded from molds and cannot be directly printed.

It is therefore an object of the invention to specify a method and anapparatus for producing a component by means of an additivemanufacturing process in which an initially liquid raw material can beused as the material to be processed. Furthermore, it is intended that amedical implant be specified which can be manufactured from such amaterial by means of an additive manufacturing process.

This object is achieved as claimed in claim 1 by a method for producinga component by means of an additive manufacturing process, wherein thecomponent is entirely or partly produced from a liquid raw materialsolidifiable by heating, wherein the raw material is dispensed in liquidform into a manufacturing zone and is, as a result ofcomputer-controlled, punctual targeted light irradiation, heated andthereby solidified, by the impact point of a light beam of a light-beamsource relative to the manufacturing zone being altered in a continuousand/or in a step-by-step manner.

The invention solves a substantial problem which occurs in the use of aliquid raw material without the aid of a negative mold, namely that theraw material flows away or flows apart relatively rapidly from theapplication point. The invention solves this by computer-controlled,punctual targeted light irradiation and also by the fact that the rawmaterial used is a raw material solidifiable by heating. As a result,the raw material applied in liquid form can be cured in a targetedmanner relatively rapidly at least to the extent that it maintains itsshape and no longer flows away.

A further advantage is that it is possible to use raw materials whichcannot be cured by ultraviolet light irradiation, i.e., which do notcomprise UV crosslinkers. As a result, it is possible in manyapplications to produce better tolerable components, especially medicalimplants. As raw material, it is possible to use, in particular, medicalmaterials which are already authorized.

The problem mentioned at the start in the use of liquid raw material issignificant in the production of flexible implants, since a manufactureof individually matched polymer-based implants did not appear possibleuntil now. It is desired that, for an optimal effect, solid and alsoflexible implants should be matched to and positioned at the individualtarget site of each individual patient as specifically as possible. Ifthis is not the case, the implant can, in the worst case, not only failto fulfill its intended function, but also damage healthy structures andprocesses. A pacemaker electrode, an electrode shaft of a cochlearimplant, a probe for deep brain stimulation or an implant for corticaldischarge would be of little use if their electrode contacts were not tobe positioned in the immediate surroundings of the targeted cells. Thus,a method which, in addition to the production of anatomically matchedimplants from solid materials, also allows the production from flexiblematerials would be ideal. Furthermore, materials which are alreadyavailable should be able to be processed, since only photosensitiveplastics can be processed using the aforementioned methods. In medicaltechnology, this strongly limits especially the choice of material,since plastics which are photosensitive and simultaneously biocompatibleare rare. When using UV crosslinkers, common materials such as, forexample, silicone elastomers (application in breast implants, cochlearimplant systems, probes, pacemakers, etc.) can only be used inshort-term applications, since the UV crosslinkers are not authorizedfor long-term applications. By contrast, silicone elastomers whichcrosslink due to heat have been tested and are already authorized forlong-term application.

As already mentioned, the impact point of the light beam of thelight-beam source relative to the manufacturing zone is altered in acontinuous and/or in a step-by-step manner. For example, this can beachieved by the light-beam source being controllable with respect to thebeam direction of the light, and so the beam direction of the light beamis altered in a continuous and/or in a step-by-step manner and differentsites of the manufacturing zone are thus irradiated. Alternatively or incombination therewith, it is also possible for the manufacturing zone tobe alterable in position, for example in the form of a table which ismovable in at least two directions in space and on which the componentto be additively manufactured is constructed.

The manufacturing zone can be in particular a manufacturing zone of anapparatus for producing a component by means of an additivemanufacturing process, for example a planar or curved surface on whichthe raw material is dispensed and where the component then arisesadditively.

According to an advantageous development of the invention, thesolidified raw material further has a high elasticity. This has theadvantage that it is possible with the invention to produce flexible orhighly elastic components, such as, for example, soft-tissue implantsfor the medical area. The solidified raw material can be in particular arubbery-elastic material. According to an advantageous development ofthe invention, the solidified raw material has a Shore hardness withinthe range from 10 to 90 Shore A, more particularly 20 to 60 Shore A.

The raw material can be in particular a polymer material. In this case,the raw material in the liquid state is also referred to as prepolymer.In particular, the raw material can be a silicone material, for examplesilicone rubber. Biocompatible silicones authorized for the medical areaare in particular obligatory for the production of medical implants.

According to an advantageous development of the invention, the lightbeam of the light-beam source is formed as a finely focused light beam.In particular, the light beam can have a diameter ≦300 μm, even better≦200 μm, at the impact point on the raw material to be solidified. Thisallows the production of the component with a high three-dimensionalresolution, and so it is also possible to produce finely detailedcomponents.

According to an advantageous development of the invention, the impactpoint of the light beam of the light-beam source relative to themanufacturing zone is, during the manufacturing process for thecomponent, repositioned in relation to a raw material dispensing unitwhich dispenses the raw material in a dropwise manner, and so rawmaterial drops freshly dispensed by the raw material dispensing unit areimmediately heated and thereby solidified by the light beam. This hasthe advantage that the component can be produced especially quicklyvirtually in any desired design by point-by-point application of the rawmaterial. Owing to the heat generated for a short time by the light beamafter dispensing of a raw material drop, said drop is immediatelysolidified to the extent that it cannot flow away. The repositioning ofthe impact point of the light beam with the raw material dispensing unitcan, for example, be realized such that the light-beam source ismechanically coupled in a fixed manner with the raw material dispensingunit and that the beam direction of the light beam is alignedaccordingly, and so the light beam automatically strikes a raw materialdrop freshly dispensed by the raw material dispensing unit. It is alsopossible for the light-beam source and the raw material dispensing unitto be mechanically decoupled from one another. In this case, it isadvantageous to reposition the beam direction of the light beam of thelight-beam source in relation to the raw material dispensing unit in acomputer-controlled manner.

According to an advantageous development of the invention, the liquidraw material in the raw material dispensing unit is already preheatedbefore dispensing and thus partially solidified by means of a preheatingunit. This has the advantage that the viscosity of the liquid rawmaterial can be somewhat increased in advance (prevulcanization) andthus the energy input to be generated by the light beam after dispensingof the raw material from the raw material dispensing unit is reduced. Asa result, it is possible to increase the working speed and precision ofthe additive manufacturing process.

According to an advantageous development of the invention, the rawmaterial is mixed with a curing-promoting material. For example, thiscan be done in advance, i.e., before the raw material is used in theadditive manufacturing process, for example by the manufacturer, orduring the additive manufacturing process. For example, the mixing withthe curing-promoting material can be done within the raw materialdispensing unit via a mixer arranged therein. The admixing of acuring-promoting material has the advantage that the energy input to begenerated by the light-beam source in order to solidify the liquid rawmaterial is reduced. This is likewise advantageous for a high workingspeed and precision of the additive manufacturing process.

According to an advantageous development of the invention,light-absorbing particles are admixed as curing-promoting material,which particles increase the light absorption of the thus formed massand thus quicken the solidification due to light irradiation.

According to an advantageous development of the invention, the lightbeam is an infrared light beam or has at least predominantly infraredspectral components. This has the advantage that a high heatingefficiency in the raw material to be solidified can be achieved by meansof the light-beam source. For example, the light-beam source can be alaser light source, for example an infrared laser diode, a carbonmonoxide laser or a CO2 laser. A ceramic infrared emitter is furthersuitable. The desired, finely focused light beam of the light-beamsource can also be generated via a suitable optics system, for example alens system.

According to an advantageous development of the invention, the componentis produced with multiple functional layers, by particular layers beingapplied by the application of a further raw material to alreadysolidified regions of the component, which layers are in turn solidifiedby computer-controlled targeted light irradiation. As already explainedabove, the application of the further layers can likewise be effected ina point-by-point manner.

According to an advantageous development of the invention, the componentis produced from multiple different materials, with at least one holdingstructure for at least one further subelement of the component beinggenerated from the raw material solidified by light irradiation. In thisway, it is also possible to generate complex technical components,especially also components having electrically conductive structures. Inthis way, it is possible to generate, for example, subdural electrodearrays by means of the invention. In this case, the further materialsused, which are used besides the liquid raw material, need notnecessarily be generated concomitantly in the same additivemanufacturing process as the actual component; instead, they can also beprovided as prefabricated parts, for example in the form of metallattice arrays.

According to an advantageous development of the invention, the rawmaterial is not completely solidified by means of thecomputer-controlled, punctual targeted light irradiation in a firstpass. This has the advantage that the manufacturing process can befurther quickened. The residence time of the light beam at a particularraw material point can be reduced as a result. A further advantage isthat the raw material can, as a result of its incomplete solidification,have properties which are favorable for the adhesion of a furtherapplied layer of the raw material.

After carrying out the stated first pass, it is possible to effect afurther or final solidification of the raw material in a second pass.For example, this can be effected by general heating of the otherwisealready completely manufactured component, for example in an oven, or byrenewed punctual light irradiation, with again the impact point of thelight beam relative to the manufacturing zone or to the componentalready now present being altered. In the second pass, the light beamcan be less finely focused, i.e., have a larger diameter in the impactpoint than in the first pass.

According to an advantageous development of the invention, the componentis subjected to a heat after-treatment after complete or partialconclusion of the solidification process for the liquid raw material inthe second pass by computer-controlled, targeted light irradiation.

The manufacturing zone can have in particular a platform on which thecomponent is generated. For instance, the component can be produced bycomputer-controlled point-by-point application of the liquid rawmaterial to the platform and/or to already solidified raw material andsubsequent solidification due to light irradiation of a particular rawmaterial point which is still liquid.

According to an advantageous development of the invention, one or moreliquid raw material points are applied to the platform and/or to alreadysolidified raw material and are solidified by light irradiation beforefurther points of liquid raw material are applied. This also counteractsflowing away of the liquid raw material, by it being quickly heated andthus solidified in a point-by-point manner.

According to an advantageous development of the invention, the liquidraw material is applied in a layer-by-layer manner to a platform and/orto already solidified raw material and is solidified bycomputer-controlled, targeted light irradiation before a further layerof liquid raw material is applied. In contrast to the point-by-pointapplication of the raw material, the layer-by-layer application has theadvantage that the working speed of the manufacturing process can befurther increased. Excess raw material not solidified by the light beamcan then be later removed.

According to an advantageous development of the invention, the platformis lowered each time after the application of one or more layers of theraw material. In this way, the raw material dispensing unit need not bedesigned to be movable in all three directions in space; instead, itcan, for example, be movable only in one plane, i.e., in two directionsin space. This simplifies the mechanics of an apparatus for producingthe component.

According to an advantageous development of the invention, the liquidraw material is solidified by multiple light beams which intersect inone point of the raw material, which point is to be solidified. This hasthe advantage that other regions of the raw material that are alreadysolidified are not undesirably heated. Moreover, this can also increasethe working speed of the additive manufacturing process. Theintersecting light beams can, for example, be emitted by two separatelycomputer-controlled light-beam sources.

According to an advantageous development of the invention, in one ormore regions of the component to be produced, electrically conductivematerial is admixed with the raw material in the liquid state. In thisway, it is possible to form certain regions of the produced component aselectrically conductive regions. The electrically conductive material isheld at a defined position in the produced component by the raw materialin the solidified state. As electrically conductive material, it ispossible, for example, to use carbon nanotubes. The mixing with theelectrically conductive material can be done within the raw materialdispensing unit via a mixer arranged therein.

According to an advantageous development of the invention, the emissionof light from the light-beam source to the raw material is switched onand off by means of a shutter. This has the advantage that it is alsopossible to use those light-beam sources where the switch-on andswitch-off process is tainted by relatively huge dead times, such as,for example, electrically heated spiral-wound filaments. When usinglaser diodes as light-beam source, such a shutter will not be necessaryin many cases, but can nevertheless also be used advantageously in suchcases.

According to an advantageous development of the invention, the componentis, as a result of controlling the targeted light irradiation, producedwith elasticity values of the solidified material that differ fromregion to region. This has the advantage that one component can beproduced from the same raw material, which ultimately has a desiredinhomogeneous elasticity distribution. Here, the material-specificelasticity can in particular vary in different regions of the component.

The object stated at the start is further achieved by an apparatus forproducing a component by means of an additive manufacturing process,comprising:

-   -   a) a manufacturing zone at which the component to be produced is        formed by means of raw material which is to be arranged there,        which is liquid and which is solidifiable by heating,    -   b) a raw material dispensing unit for dispensing the raw        material to the manufacturing zone,    -   c) a light-beam source for emitting a light beam,    -   d) a controllable actuator mechanism which makes it possible to        alter the impact point of the light beam of the light-beam        source relative to the manufacturing zone in a continuous and/or        in a step-by-step manner,    -   e) a control unit with a computer, which control unit is        configured to control the actuator mechanism,    -   f) wherein the apparatus is configured to carry out a method for        producing a component by means of an additive manufacturing        process of the type explained above.

Using such an apparatus, it is likewise possible to realize theadvantages stated above with regard to the method. The above-explainedequipment-based developments of the invention, too, are also realizableas advantageous developments of the apparatus. In particular, theapparatus can comprise a shutter. The shutter can be controllable bymeans of the control unit. Furthermore, the apparatus can comprisemultiple light-beam sources which are controllable with respect to thebeam direction. The light-beam sources can, with respect to their beamdirection and/or with respect to the emission of light (brightness orswitching on/switching off of the emission of light), be controllable bythe control unit. The light-beam source can be an infrared light-beamsource or have at least predominantly infrared spectral components inthe emitted light. In particular, the light-beam source can be designedas a laser light source.

The object stated at the start is further achieved by a medical implantgenerated for an individual patient, composed of rubbery-elasticmaterial without a stabilizing scaffolding structure, having one or moreelectrodes which are embedded in the rubbery-elastic material and which,at least at a particular external contact surface, are not covered bythe rubbery-elastic material. Such a medical implant can be producedadditively, for example using a method by means of an additivemanufacturing process of the type explained above and/or using anapparatus of the type explained above. In this way, medical implants forindividual patients can be provided efficiently, precisely and rapidly.The medical implant has a pixel structure owing to the additiveproduction. However, this is practically imperceptible, at least notdisturbing, in the case of an appropriately high resolution of theadditive manufacturing process, i.e., when using a finely focused lightbeam and accordingly small impact points of the light beam on the rawmaterial to be solidified. The rubbery-elastic material of the medicalimplant can have a Shore hardness within the range from 10 to 90 ShoreA, more particularly 20 to 60 Shore A. The implant can be formed in amultilayer manner with multiple functional layers.

According to an advantageous development of the invention, the implantis designed as an ECoG electrode array, as a pacemaker electrode array,as a cochlear implant electrode array or as a brainstem implantelectrode array.

According to an advantageous development of the invention, one, more orall electrodes of the implant are formed by electrically conductivematerial admixed loosely with the rubbery-elastic material of theimplant. As electrically conductive material, it is possible to use thecarbon nanotubes already mentioned. In this way, the final implant withthe electrodes continues to maintain its overall highly elasticproperties.

According to an advantageous development of the invention, the implanthas specific elasticity values of the rubbery-elastic material thatdiffer from region to region. In this way, the implant can, depending onthe application, also be adjusted with respect to its elasticproperties, for example having external, more elastic regions and acentral region with a lower specific elasticity.

The invention provides further advantages. Just through the possibilityof being able to use established and authorized plastics, it is possibleto realize the production of new products which, especially in medicaltechnology, can be produced with distinctly reduced development andauthorization costs. Furthermore, the proposed invention allows themanufacture of personalized implants which promise a distinctly improvedmatch to the anatomy of the patient. This entails distinct advantageswhich are to be shown in the following application examples. Besides thestated system-related advantages, the crosslinking by means of IRradiation has the method advantage that the irradiated volume iscrosslinked in a location-independent manner and is thus not bound toheat conduction and convection through the surface. This allows,firstly, a more rapid crosslinking, a potentially higher crosslinkingtemperature and, associated therewith, a quickened rise in viscositythat significantly increases the shape accuracy of the component.

The following embodiments of the invention are also advantageous:

-   -   1. A method for producing a printed component, characterized in        that the component body is produced from a polymer which        crosslinks due to heat and which is crosslinked by means of        targeted infrared irradiation.    -   2. A base body produced in accordance with The method as claimed        in embodiment 1, characterized in that multiple functional        layers are generated by the application of further polymers        which crosslink due to heat and which are crosslinked by        targeted infrared irradiation.    -   3. A base body produced in accordance with The method as claimed        in embodiment 1, characterized in that the polymer which        crosslinks due to heat is crosslinked by irradiation with an        infrared laser, carbon monoxide laser, a CO2 laser, infrared        diode and a ceramic infrared emitter.    -   4. A base body produced in accordance with The method as claimed        in embodiment 1 or 2, characterized in that the base body is        produced by point-by-point application of the prepolymer to a        planar platform and subsequent crosslinking, in line with        embodiment 3.    -   5. A base body produced in accordance with The method as claimed        in embodiment 1 or 2, characterized in that the base body is        produced by point-by-point application of the prepolymer to a        structured platform and subsequent crosslinking, in line with        embodiment 3.    -   6. A base body produced in accordance with The method as claimed        in embodiment 1 or 2, characterized in that the base body is        produced by layer-by-layer application of the prepolymer to a        straight lowerable platform and subsequent crosslinking, in line        with embodiment 3.    -   7. A base body produced in accordance with The method as claimed        in embodiment 1 or 2, characterized in that the base body is        produced by layer-by-layer application of silicone rubber        prepolymer and subsequent crosslinking, in line with embodiment        3.

The invention will be more particularly elucidated below on the basis ofexemplary embodiments with use of drawings, showing

FIG. 1—3D printing method for multicomponent components withlayer-by-layer polymer application (left, FIG. 1a )) and point-by-pointpolymer application (right, FIG. 1b )). The system for layer-by-layerpolymer application comprises: a lowerable platform 15, the solidifiedcomponent 10, the infrared laser 3, multiple wipers 17 for applying theprepolymers. The uncrosslinked prepolymer 12 must be removed at the endof the process. The system for point-by-point polymer applicationcomprises: a fixed platform 15, the vulcanized component 10, theinfrared laser 3 and printheads/dispensers 2 for applying theprepolymers.

FIG. 2—Cortex surface 30 with an individually matched 4-contact gridelectrode array 20. The drawn-in sectional view A-A is depicted in FIG.3.

FIG. 3—Sectional view A-A of the brain 30 with a conventional (rigid)4-contact grid electrode array 31 (left, FIG. 3a ) and enlarged view atthe center (FIG. 3b ) and a personalized flexible 4-contact gridelectrode array 20 (right, FIG. 3c )). The rigid grid electrode array 31does not match the sulci 32 and gyri 33 of the cortex surface. Thepersonalized grid electrode array 20 allows a better match to the cortextopography.

FIG. 4—Sectional view A-A (left, FIG. 4a )) of the brain 30 withintended implant position for the personalized grid electrode array 20and 3D printing method (right, FIG. 4b )) with individually manufacturedprinting underlay 1, printed implant 20, movable infrared laser 3 andmovable printheads/dispensers 2 for applying the prepolymers to theprinting underlay.

FIG. 5—A schematic depiction of an apparatus for producing a componentby means of an additive manufacturing process.

FIG. 6—A personalized grid electrode array 20.

In the figures, the same reference signs are used for elements whichcorrespond to one another.

Besides the elements already mentioned, FIG. 1a ) shows that thecomponent 10 is produced as a medical implant with embedded electrodes.Within the rubbery-elastic material of the component 10, a metalstructure 18 is present for forming the electrodes. Owing to the lightbeam 8 emitted by the light-beam source 3, there is a solidification ofthe prepolymer which is still liquid. The platform 15 is situated in amanufacturing zone 1 of an apparatus for producing the component 10.

In FIG. 1b ), the abovementioned dispensers 2 form a raw materialdispensing unit for the dropwise dispensing of the liquid raw material.

FIG. 2 shows a medical implant 20 generated for an individual patientand applied to a brain surface 30, in the form of an electrode array inwhich there are electrodes 21 which are embedded in rubbery-elasticmaterial and which are electrically contactable via electricalconnecting lines 24. The implant does not have a stabilizing scaffoldingstructure and can thereby be matched especially flexibly to the brainsurface. The electrodes and also the connecting lines 24 can be formedfrom the abovementioned metal structure 18.

As mentioned, it is advantageous that already established materials canbe used for the direct additive manufacture of individual structures.

Especially in medical technology, this will distinctly reduce thedevelopment and authorization costs, since no new materials need to bedeveloped and authorized. We therefore propose the production offlexible structures/implants from already established plastics whichcrosslink due to heat and which, in the liquid state, are crosslinked ina shape-faithful manner by the action of an infrared radiationspectrally matched to the specific absorption behavior of the plastic.The basis thereof is the proven selective absorption behavior of commonplastics, such as, for example, polydimethylsiloxane or polyvinylchloride in the long-wave IR range, which can, inter alfa, be generatedby means of IR diodes, ceramic emitters and various laser systems. Forthe targeted crosslinking of fine structures, laser systems (acting in apoint-by-point manner) are advantageous in particular, since IR diodesare currently not efficient enough and ceramic emitters are, owing totheir diffuse radiation, complicated to focus. Thus, in a 3D printingmethod, the prepolymer can be applied to a platform with layer-by-layeror point-by-point polymer application and be crosslinked in apoint-by-point manner using a movable infrared laser; see FIG. 1.Similarly to stereolithography, the layer-by-layer polymer application(FIG. 1a ), left) is done via various wipers 17 on a lowerable platform15. In the case of the point-by-point polymer application (FIG. 2,right), movable extruder or dispenser devices 2 are advantageous, whichdevices allow an exact dispensing of the applied prepolymer to theplatform 15. Unaffected thereby, an area-by-area crosslinking can becarried out in both cases, it being necessary to fundamentally note thatthe shape accuracy depends on any absorbed temporal surface energy andthe rheological crosslinking behavior of the plastic.

Within the scope of a further design of the invention, it is possible toevaluate the manufacturability of composite materials and ofmulticomponent components. In this regard, the use of multi-extruders orpiezo-based or ultrasound-based printheads is advantageous. In addition,it is conceivable to add IR-absorbing particles which, when introducedinto the prepolymer, increase the absorbed beam power.

Exemplary Embodiment 1 Use of the Proposed Invention as a StripElectrode or Grid Electrode for Subdural Discharge and Stimulation

With respect to the prosthetic treatment of motor-impaired patients, andalso for the diagnosis and therapy of diseases of the cerebral cortex,it is conceivable to use long-term stable subdural electrodes which candischarge (electrocorticogram) and stimulate (subdural microstimulation)(J. E. O'Doherty, M. A.

Lebedey, T. L. Hanson, N. A. Fitzsimmons and M. A. L. Nicolelis,Frontiers in Integrative Neuroscience 3, 1-(2009), U.S. Pat. No.7,120,486 B2). As a result, it is possible to create a bidirectionalinterface for recording movement intentions and for applying asomatosensory feedback, which interface can be used for the intuitivecontrol of prostheses and orthoses. An ideal of said subdural electrodesare so-called electrocortical grid arrays (ECoGs), which have alreadybeen used clinically for 20 years for presurgical diagnostics forepilepsy patients. ECoGs are silicone-based lamellar neural implantswhich are directly positioned on the surface of the brain. Owing to amultiplicity of electrodes embedded in the silicone, usually composed ofplatinum materials or stainless steels, it is possible to measureelectrical activities of the cerebral cortex and to transmit them viaconnecting lines (pigtail harnesses, cable harnesses) to a measurementcomputer. The available systems are not suitable for a prosthetic andtherapeutic treatment, since they do not stimulate, do not provide fineresolution, and cannot match the individual anatomical structures of thepatient. Thus, ECoGs are typically manufactured in fixed dimensionswhich fit “average patients”, but do not take into account theindividual topography of the brain of each patient. They have between 4and 64 electrode contacts, a contact diameter of 2 mm, 3 mm or 4.5 mmand a thickness of about 1.5 mm (A. Sinal, C. W. Bowers, C-M.Crainiceanu, D. Boatman, B. Gardon, R. P. Lesser, F. A. Lenz and N. E.Grone, Brain 128, 1556-1570 (2005); Cortac® Epilepsy Electrodes, PMTCorporation, Chanhassen, USA; Adtech, Racine, USA). This is significant,since the attachment of electrodes to nerve structures strongly dependson the “perfect fit” of the electrode layer. For example, Formaggio etal. (2013), in their study concerning discharge by means of ECoG withsimultaneous stimulation of the primary motor cortex and of the primarysensory cortex, find that the attained discharge areas and the positionsof the electrode contacts of the conventional ECoG used distinctlydiffer among the patients examined because of the individual position ofthe motor cortex (E.

Formaggio, S. F. Storti, V. Tramontano, A. Casarin, A. Bertoldo, A.Flaschi, A. Talacchi, F. Sala, G. M. Toffolo and P. Mananotti, Frontiersin Human Neuroscience 6, 1-8 (2013)). On this basis, an adequatetreatment of all patients is not achieved with standard implants.

With the proposed invention, it is possible to manufacture previouslyunavailable patient-personalized subdural electrode systems which can beutilized for diagnostics, therapeutics and prosthetics; see FIG. 2 andFIG. 3. To this end, it would be possible, on the basis of 3D volumedata sets of the patient with use of computer-aided manufacturingtechniques (CAM techniques), to model and develop grid electrode arrayswhich are matched to the anatomy of the patient. It would subsequentlybe possible to manufacture these in a 3D printer modified for siliconeprinting. To this end, firstly, the implant base body composed of abiocompatible silicone rubber which crosslinks on the basis oftemperature is sprayed onto a printing bed using a movable dispenser andsimultaneously vulcanized within a few seconds using a movable infraredlaser beam. Experiments have shown that a vulcanization of a 2 mm thicksilicone sample can be carried out in less than 45 seconds. This timecan be distinctly enhanced again with thinner samples and an optimizedheat-transfer behavior. This means that infrared crosslinking is alreadydistinctly below the manufacturer-specified vulcanization times of morethan 15 minutes. In this connection, the printing bed can have theintended shape of the implant (see FIG. 4) or a straight shape, and inthis case the intended 3D structure must be projected onto the 2D planeof the printing bed. Subsequently, in the next step, the conductormaterial (e.g., silver conductive paste) can be applied using a seconddispenser to the base shape generated. Afterwards, in the last step ofthe method, silicone rubber is sprayed and crosslinked, and so theconductor material is completely encapsulated in silicone.Alternatively, the implant can be produced in a lowerable prepolymerbath by layer-by-layer in situ vulcanization. Occasionally, what iscrucial for the shape accuracy and the resolution of the method is thedistinct demarcation of the vulcanized material from the prepolymer. Tothis end, the diameter of the laser beam should be matched to the sizeof the target structures. Since the silicone rubber already crosslinksat room temperature, the production process should be carried outquickly in order to achieve a strict discrimination between prepolymerand component. Alternatively, in the case of crosslinking in a polymerbath, it is possible to use, instead of a high-performance laser,multiple weaker lasers having the same focal point but different beampaths, and so primarily only the volume to be crosslinked and not theedge regions are irradiated.

The apparatus depicted in highly schematic form in FIG. 5 for theproduction of a component 10 comprises the following components: amanufacturing zone 1 having a platform 15, a raw material dispensingunit 2, a light-beam source 3, a shutter 4, a control unit 5 with acomputer 16, an actuator mechanism 6 and a heat source 7. For example,the component 10 is produced in the manufacturing zone 1 on the platform15 by means of the additive manufacturing process. To this end, the rawmaterial dispensing unit 2 dispenses, from raw material 12 keptavailable in liquid form therein, raw material drops 9. After theyimpact in the manufacturing zone 1, the raw material drops 9 are heatedand thus solidified by a light beam 8 of the light-beam source 3. Tocarry out the additive manufacturing process, it is necessary to alterthe position of the raw material dispensing unit relative to themanufacturing zone 1 or to the component 10 already produced in partthereon. In this case, the light-beam source 3 must be repositioned tothe same extent. The actuator mechanism 6 serves for this purpose. Forexample, said mechanism can be designed such that the manufacturing zone1 is, for example, moved in two directions in space in a horizontalplane. In addition, a possibility for adjustment in the third directionin space, i.e., upward and downward, can also be present. Alternativelyor additionally, the actuator mechanism 6 can also alter the light-beamsource 3 and the raw material dispensing unit 2 with respect to theirposition.

The control unit 5 controls the entire manufacturing process such thatthe individual method steps are controlled by a computer 16 on which acomputer program runs, for example by the raw material dispensing unit 2for dispensing a raw material drop 9 being controlled and the actuatormechanism 6 for the appropriate positioning of the individual componentsbeing controlled. Moreover, it is possible, via the control unit 5, tocontrol the light-beam source 3 with respect to the light emission ofthe light beam 8, for example by switching-on and switching-off of thelight beam 8. If a light-beam source 3 is used in which the switching-onand switching-off of the light beam 8 cannot be done within thenecessary short time, the shutter 4 can be additionally used. Saidshutter acts as a screen introducible into the light beam 8, and so, bymechanical actuation of the shutter 4, for example from the actuatormechanism 6, the light beam 8 of the light-beam source 3 can beinterrupted for a short time and be uninterrupted again.

The raw material dispensing unit 2 can comprise a preheating unit 13 bymeans of which the liquid raw material 12 can be already preheated andthus partially solidified in the raw material dispensing unit 2.Furthermore, the raw material dispensing unit 2 can comprise a reserveof curing-promoting and/or electrically conductive material 14 which canbe admixed with the raw material 12 via a mixer. In this way, it ispossible, for example, to admix carbon nanotubes for the production ofconductive regions of the component 10 with the raw material 12 asrequired.

The heat source 7 is intended for achieving a conclusive complete curingof the raw material. Said curing can likewise be controlled via thecontrol unit 5, for example be switched on and switched off. By means ofthe heat source 7, heat radiation 11 is radiated onto the component 10,making it possible to achieve a heat after-treatment of the component10.

FIG. 6 shows the medical implant in the form of the grid electrode array20 additionally in a sectional view from the top and in across-sectional view in the section plane B-B (bottom part of FIG. 6).In this case, it is possible to discern six electrodes 21 which areelectrically contacted via connecting lines 24. The connecting lines 24are guided out of the rubbery-elastic material 23 of the implant at aconnection side. Furthermore, it is possible to discern that aparticular external contact surface 22 of the electrodes 21 is notcovered by the rubbery-elastic material 23, ensuring a good electricalcontacting in relation to the tissue surface of the patient.

1. A method for producing a component by an additive manufacturingprocess, wherein the component is entirely or partly produced from aliquid raw material solidifiable by heating, the method comprisingdispensing the raw material in liquid form into a manufacturing zone,and heating and thereby solidifying the raw material, as a result ofcomputer-controlled, punctual targeted light irradiation, by the impactpoint of a light beam of a light-beam source relative to themanufacturing zone being altered in one or more of a continuous mannerand a step-by-step manner.
 2. The method as claimed in claim 1, whereinthe raw material (12) is a polymer material.
 3. The method as claimed inclaim 1, further comprising repositioning the impact point of the lightbeam of the light-beam source relative to the manufacturing zone duringthe manufacturing process for the component, wherein the impact point ofthe light beam is repositioned in relation to a raw material dispensingunit which dispenses the raw material in a dropwise manner such that rawmaterial drops freshly dispensed by the raw material dispensing unit areimmediately heated and thereby solidified by the light beam.
 4. Themethod as claimed in claim 1, further comprising preheating, by apreheating unit, the liquid raw material in a raw material dispensingunit is before dispensing such that the liquid raw material is partiallysolidified.
 5. The method as claimed in claim 1, further comprisingmixing the raw material with a curing-promoting material.
 6. The methodas claimed in claim 1, wherein the light beam is an infrared light beamor has at least predominantly infrared spectral components.
 7. Themethod as claimed in claim 1, further comprising producing the componentfrom multiple different materials, with at least one holding structurefor at least one subelement of the component being generated from theraw material solidified by light irradiation.
 8. The method as claimedin claim 1, wherein the raw material is not completely solidified bymeans of the computer-controlled, punctual targeted light irradiation ina first pass.
 9. The method as claimed in claim 1, further comprisingapplying one or more liquid raw material points to one or more of aplatform and already solidified raw material, and solidifying the one ormore liquid raw material points by light irradiation before furtherpoints of liquid raw material are applied.
 10. The method as claimed inclaim 1, further comprising applying the liquid raw material in alayer-by-layer manner to one or more of a platform and alreadysolidified raw material, and solidifying the applied liquid raw materialby computer-controlled, targeted light irradiation before a furtherlayer of liquid raw material is applied.
 11. The method as claimed inclaim 1, further comprising subjecting the component to a heatafter-treatment after complete or partial conclusion of the heating andsolidification step for the liquid raw material by computer-controlled,targeted light irradiation.
 12. An apparatus for producing a componentby means of an additive manufacturing process, comprising: amanufacturing zone at which the component to be produced is formed byraw material which is to be arranged there, which is liquid, and whichis solidifiable by heating, a raw material dispensing unit fordispensing the raw material to the manufacturing zone, a light-beamsource for emitting a light beam, a controllable actuator mechanismwhich allows altering the impact point of the light beam of thelight-beam source relative to the manufacturing zone in one or more of acontinuous manner and a step-by-step manner, and a control unit with acomputer, wherein the control unit is configured to control the actuatormechanism wherein the apparatus is configured to carry out a method forproducing a component by an additive manufacturing process, wherein thecomponent is entirely or partly produced from a liquid raw materialsolidifiable by heating, the method comprising dispensing the rawmaterial in liquid form into the manufacturing zone, and heating andthereby solidifying the raw material, as a result ofcomputer-controlled, punctual targeted light irradiation, the impactpoint of a light beam of the light-beam source relative to themanufacturing zone being altered in one or more of a continuous mannerand a step-by-step manner.
 13. A medical implant generated for anindividual patient, comprising rubbery-elastic material without astabilizing scaffolding structure, and one or more electrodes which areembedded in the rubbery-elastic material and which, at least at aparticular external contact surface, are not covered by therubbery-elastic material.